Roll assembly carrier mounting for pulverizing mills



y 1950 w A GIBSON 2,506,499

ROLL ASSEMBLY CARRIER MOUNTING FOR PULVERIZING MILLS Filed June 26, 1947 muw %-:Z

Patented May 2, 1950 ROLL ASSEMBLY CARRIER MOUNTING FOR PULVERIZING MILLS William A. Gibson, Allentown, Pa., assignor to Bradley Pulverizer Company, Boston, Mass, a

corporation of Massachusetts Application June 26, 1947, Serial No. 757,235

3 Claims.

This invention relates to pulverizing mills of the general type described in Patent No. 826,060 of George Lewis Pratt, granted July 17, 1906, in which a series of crushing roll assemblies hinged to a rotatable carrier member are urged centrifugally against an annular die ring, the coarse material to be pulverized (such as limestone, cement rock or the like) being fed between the crushing rolls and the die ring to accomplish the reduction thereof.

In mills of this general type the roll assembly carrier member, hereinafter called the carrier, is

' attached to the lower end of a vertically disposed center driving shaft which is suspended for rotation within the machine frame, as disclosed in the above-mentioned patent of Pratt. The carrier with its roll assemblies may weigh several tons and (because the carrier occupies a position in the upper part of the pulverizing chamber) may be exposed to high temperatures when the mill is used for the grinding of warm or hot materials. In addition, the carrier is subjected to severe shocks and stresses which result from the normal operation of the mill.

A heretofore common mode of mounting the carrier on the center shaft has comprised inserting the tapered lower end of the center shaft into a correspondingly tapered bore in the hub of the carrier and holding the carrier in place by means of a nut or other fastening secured upon the projecting lower end of the center shaft, as shown by the above-mentioned patent of Pratt. The disadvantage of this mode of attachment is that the carrier, under the influence of the high temperature conditions prevailing within the pulverizing chamber, expands and loosens upon its shaft and begins to wobble and gyrate. In consequence of its massive weight and the vibrations to which it is subjected during operation of the mill, the carrier rapidly chews away the shaft until the latter becomes dangerously weakened or fails altogether. Also, because the nut supports the entire weight of the carrier with its roll assemblies, there is the possibility of the nut loosening upon the shaft as a result of shock and vibration and breaking its fastening, thus allowing the carrier to drop off the end of the shaft into the bottom of the pulverizing chamher. When looseness of the carrier upon the shaft is discovered in time, this condition may be corrected by tightening the nut to draw the carrier firmly onto the shaft, although this requires that the mill be shut down with a consequent loss of production to permit the mill to cool off sufiiciently to allow the necessary nut adjustment to be made.

It is an important object of the present invention to provide in a pulverizing mill of the above character improved means for mounting the roll assembly carrier upon the center driving shaft which avoids the objections pointed out above. This object is accomplished by securing the carrier to the center shaft in a manner such that the weight of the carrier and its roll assemblies act to clamp the carrier to the shaft and also to automatically take up any play that may develop between the carrier and the shaft during operation of the mill.

In accordance with the preferred form of my invention, the nut or other fastening means located below the carrier on the center shaft is relieved of all weight of the carrier, and may actually be dispensed with if desired.

Another object of the invention is to provide in a pulverizing mill of the above character, conveniently operable means for raising or lowering the carrier on the center shaft to properly adjust the path of contact of the rolls with respect to the annular die ring, thus insuring the most eflicient grinding operation.

Still another object of the invention is to provide in a pulverizing mill of the above character a longitudinally-split downwardly and outwardi ly-tapered adapter member threaded upon the lower end of the shaft and interfitting within a correspondingly tapered opening in the carrier for supporting the carrier, whereby the weight of the carrier and roll assemblies acts to compress the adapter into tight binding engagement with the shaft. In the preferred form of the invention the direction of the threads on the shaft and adapter are so directed relative to the normal direction of rotation of the shaft as to tend to screw the adapter upwardly upon the shaft when the mill is in operation which movement is prevented by a stop suitably provided to determine the position of adjustment of the adapter, and hence of the carrier and roll assemblies supported on the adapter, along the shaft.

Other objects and advantages will be apparent from the following detailed description of a preferred embodiment of the invention, reference being had to the accompanying drawing in which:

Figure 1 is a vertical cross-sectional view of a pulverizing mill of the centrifugal type, show ing the rotary center driving shaft and the roll assembly carrier member secured to its lower end;

Figure 2 is a detail view showing the means for fastening the carrier to the center shaft and also showing the stop nut for determining the position of the adapter on the center shaft; and

Figure 3 is a perspective view showing the adapter forming a part of the carrier fastening means.

In the pulver-izing mill illustrated in Fig. 1 of the drawing, a center shaft .|;;is supported vertically upon an anti-friction bearing 2 mounted in a casting 3 bridging the upper end of a machine frame 4. The center shaft is rotated by a drive shaft 5 through the intermediary of a beveled pinion 6 on the drive shaft meshing with a bevel ring gear I fixed on the center shaft i adjacent its upper end. The shaft 5 is here shown as adapted to bedriven by a pulley P although it may be driven in any other suitable manner. To the lower free end of the center shaft, which projects downwardly into the housing 8 surrounding the pulverizing chamber, is fastened a casting constituting a roll assembly carrier member 9 adapted to rotate with the center shaft. Each roll iii of a series of crushing roll assemblies (only one roll assembly being shown in the drawing) is rotatably suspended from a rocker head l2 hinged upon a trunnion shaft [3 on the carrier member. During rotation of the center shaft and carrier, the rolls ifl swing outwardly under the influence of centrifugal force and ride against an annular die ring associated with the machine frame in a horizontal plane within the pulverizing chamber. Thus the material to be pulverized when introduced into the chamber and directed between the rolls and die ring will be crushed by the rolls. Plows 55 (only one of which is shown) are mounted upon the carrier member in advance of the rolls for stirring up the material undergoing crushing. The pulverized material may be drawn off through a screen It surrounding the crushing chamber. The bottom of the pulverizing chamber is closed by a base casting I! which supports the die ring 84. The mill may rest upon a concrete foundation I! which is formed with a pit Ha below the pulverizing chamber. I

The structure thus far generally described is already known in the pulverizing mill art and no novelty is claimed therefor. In accordance with the present invention, the lower end of the center shaft 5 is threaded as indicated at H3 in Fig. 2, and screwed onto the end of this shaft is an adapter member E9 of springable metal inthe form of a truncated cone centrally bored and threaded as indicated at 29 so as to cooperate with the screw threads on the center shaft. The direction of the threads on the center shaft l and the adapter i9 is such that in the normal direction of rotation of the center shaft during operation of the mill there is a tendency for the adapter to travel upwardly along the shaft. As best shown in Fig. 3, the adapter I8 is provided with a saw cut 2! extending lengthwise thereof so as to provide a slight gap to permit of the radial contraction of the adapter, and at a diametrically opposite point, from the saw cut 2! the adapter is grooved to define a keyway 22 extending longitudinally along its circumference. The adapter is circumferentially recessed lengthwise, as indicated at 23, to afford greater spring action for the adapter.

The adapter l9, positioned so that its circumference slopes downwardly and outwardly, is designed to be screwed onto the lower end of the center shaft l as shown in Fig. 2. The carrier member 9 is correspondingly recessed to provide a, downwardly and outwardly tapered opening 24 which fits onto and snugly embraces the adapter. The carrier is held against turning on the adapter bymeans of a key 25 slidably. fitted within the keyway 22 in the adapter and a companion keyway 26 in the wall of the opening 24 of the carrier. A look nut 2'! is threaded onto the end of theg-center shaftedgwhich projects below the adapter and this nut abuts the lower end face of the adapter. ,sectionally separable retaining ring 29 is secured to the upper face of the adapter to prevent the carier from riding upwardly along the adapter. The nut 2'! being threaded similarly to the threads IS on the center shaft I is urged upwardly into engagement with the bottom face of the adapter l9 during operation of the mill. A cotter pin 28 may be passed through a diametral opening in the lower end of thecenter shaft l to serve as an additional safeguardagainst loss of the nut.

A stop nut 30 is made of sectional construction so that it may be laterally assembled upon the center shaft above the adapter, and this stop nut is locked to the center shaft by any suitable means, herein conventionally shown as a set screw 3|.

By virtue of the construction just described, the massive weight of the roll carrier member and its -ro-ll assemblies draws downwardly on the adapter and contracts the latter into tight bindingngagenient with the threads l8 on the s haft. Any looseness or play that may develop between the adapter and its carrier member during operation of the mill, such as by reason of wear or because of expansion resulting from the high temperature within the pulverizing chamber, is automatically compensated for without the need for making any manual adjustment, so that a tight connection between the parts is maintained at all times. Because looseness of the carrier is thus prevented, the danger of the center shaft becoming dangerously weakened by the action of one part rubbing or pounding against another during operation of the mill is avoided.

To dismount the carrier member with its roll assemblies from the center shaft, access is provided to the pulverizing chamber by detaching the side sections of the housing 8 and also the screen It surrounding thepulverizing chamber. The cotter pin 28 and lock nut 21 having been disengaged from the lower end of the center shaft and thesectional ring 29 and key 25 removed from the adapter, the carrier 9 is jacked up to relieve the adapter of contractile pressure and the latter is'then unscrewed from the shaft in generally the same manner as a nut.

In order to insure the most efficient operation of the pulverizing mill, the rolls it should properly track upon the die ring 14. The vertical adjustment of the rolls may be conveniently accomplished in the pulverizing mill described above by simply screwing the adapter upwardly or downwardly along the threads l8 of the center shaft until a position is reached in 'which the rolls lie in proper tracking relationship with the die ring when the carrier is seated on the adapter. The sectional stop nut 30 is then assembled upon the center shaft-l above and abutting the ring 29 and held in its adjusted position by the set screw 3|. This fixes the maximum extent the adapter (and carrier with its roll assemblies) can rise upon the center shaft. 1

Instead of being of frusto-conical form, the

adapter may take other suitable shapes. That is, it may be ofcircular, oval, angular or other contour in transverse cross-section; and if the adapter is made of non-circular cross-section the key 25 may be dispensed with. By the term spring metal as used herein as applied to the adapter is meant metal that does not permanently deform but which possesses sufilcient springiness to return the adapter to its former shape after the adapter is compressed to close the gap defined by the split.

It will be appreciated that other changes in details of construction and design of the roll carrier mounting just described may be made, such as may occur to those skilled in the art, without departing from the spirit of my invention as set forth by the following claims.

I claim:

1. In a pulverizing mill of the type having a rotatable center driving shaft, means located above the lower end of the center shaft for supporting the center shaft in a generally vertical position and a roll-assembly carrier member mounted upon the lower free end of the center shaft, the combination with said center shaft'of means for detachably securing the roll-assembly carrier member to the center shaft, said securing means comprising a unitary, downwardly and outwardly tapered adapter composed of springable metal and split in a longitudinal direction so as to define a small gap between the opposed sides of the split, said adapter being internally threaded and encircling and threadedly secured to the center shaft, a downwardly and outwardly tapered opening in the roll-assembly carrier member providing a seat for the adapter and means for interlocking and preventing relative rotation between the roll-assembly carrier member and the adapter, whereby downward pressure of the rollassembly carrier member contracts the adapter into tight engagement with the threads on the center shaft.

2. In a pulverizin-g mill as set forth in claim 1 in which the adapter is provided with a plurality of longitudinally-extending recesses upon its outer circumference to impart additional contractability to the adapter.

aooeaoo 3. In a pulverizing mill of the type having a rotatable center driving shaft, means located above the lower end of the center shaft for supporting the center shaft in a generally vertical position and a roll-assembly carrier member mounted upon the lower free end of the center shaft, the combination with said center shaft of means for detachably securing the roll-assembly carrier member to the center shaft, said securing means comprising a unitary, downwardly and outwardly tapered adapter composed of springable metal and split in a longitudinal direction so as to define a small gap between the opposed sides of the split, said adapter being internally threaded and encircling and threadedly secured to the center shaft, a downwardly and outwardly tapered opening in the roll-assembly carrier member providing a seat for the adapter, whereby downward pressure of the roll assembly carrier contracts the adapter into tight engagement with the threads on the center shaft, means for interlocking and preventing relative rotation between the roll-assembly carrier member and the adapter, the threads upon the center shaft and .{adapter extending in such direction relative to the normal direction of rotation of the center shaft in the operation of the mill as to tend to cause the adapter to screw itself upwardly along the center shaft and a stop member fixedly secured to the center shaft above the adapter to prevent upward travel of the adapter along said center shaft.

WILLIAM A. GIBSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 56,793 Pearce July 31, 1866 427,244 Stone May 6, 1890 826,060 Pratt s July 17, 1906 827,346 Bubb July 31, 1906 1,231,744 Kennedy July 3, 1917 1,358,739 Herbst Nov. 16, 1920 1,382,606 Worton June 21, 1921 1,672,601 Brent June 8, 1928 

